Air pump

ABSTRACT

An air pump has a main frame, a first pressure cylinder, a second pressure cylinder, an outlet device, a footboard, and a pressure relief device. The outlet device is connected to and communicates with the pressure cylinders. The footboard is pivotally connected to the main frame, is securely connected to the pressure cylinders, and has two side panels and a limiting board. The pressure relief device is mounted on the outlet device near the first pressure cylinder and has a base, a ball, an adjusting rod, and an anti-slip-off element. The base is securely mounted on the side face of the outlet device that faces the limiting board, and has a leaking channel. A length of the adjusting rod that extends into the leaking channel of the base is longer than a distance that is defined between the limiting board and the anti-slip-off element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air pump, and more particularly relates to an air pump that has a pressure relief device to provide a pressure relief effect to the air pump and can be operated conveniently.

2. Description of Related Art

With reference to FIGS. 5 to 7, a conventional air pump has a main frame 90, two pressure cylinders 91, a footboard 93, an outlet device 95, and a pressure relief device 80. The pressure cylinders 91 are mounted in the main frame 90, and each pressure cylinder has a cylinder 92 and a cylinder axis extending out of the cylinder 92. The footboard 93 is pivotally connected to the main frame 90 and has two side panels 94. The outlet device 95 is connected to and communicates with the pressure cylinders 91 and has a side face and a check valve mounted in the outlet device 95.

The pressure relief device 80 is mounted on the outlet device 95 near the check valve and has a base 81, a ball 82 and an adjusting rod 83. The base 81 is mounted on the side face of the outlet device 95 and has a leaking channel communicating with the outlet device 95 and an inner thread 85 formed in the leaking channel. The ball 82 is mounted in the leaking channel of the base 81. The adjusting rod 83 is connected to the base 81 and has a head 86 and a body 87 formed on and protruding from the head 86. The body 87 abuts the ball 82 and has an external surface and an outer thread 88 formed around the external surface of the body 87. The outer thread 88 of the body 87 is screwed with the inner thread 85 of the base 81 to enable the adjusting rod 83 to rotate and to move relative to the base 81.

With reference to FIG. 7, when a user rotates the adjusting rod 83 to loosen the adjusting rod 83 from the base 81 during a pressure relief process, a distance D1 is defined between the head 86 of the adjusting rod 83 and a corresponding side panel 94 that faces to the head 86 of the adjusting rod 83, and a length of the adjusting rod 83 that extends into the base 81 is defined as D2. The distance D1 between the head 86 and the corresponding side panel 94 is longer than the length D2 of the adjusting rod that extends in the base 81. Consequently, the adjusting rod 83 may be separated from the base 81 during the pressure relief process and this is inconvenient in use.

The invention provides an air pump to mitigate or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

The main objective of the present invention is to provide an air pump that has a pressure relief device to provide a pressure relief effect to the air pump and can be operated conveniently.

The air pump in accordance with the present invention has a main frame, a first pressure cylinder, a second pressure cylinder, an outlet device, a footboard, and a pressure relief device. The outlet device is connected to and communicates with the pressure cylinders. The footboard is pivotally connected to the main frame, is securely connected to the pressure cylinders, and has two side panels and a limiting board. The pressure relief device is mounted on the outlet device near the first pressure cylinder and has a base, a ball, an adjusting rod, and an anti-slip-off element. The base is securely mounted on the side face of the outlet device that faces the limiting board and has a leaking channel. A distance of the adjusting rod that extends into the leaking channel of the base is longer than a distance that is defined between the limiting board and the anti-slip-off element.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an air pump in accordance with the present invention;

FIG. 2 is a bottom view of the air pump in FIG. 1;

FIG. 3 is a side view of the air pump in FIG. 1; and

FIG. 4 is an enlarged bottom view in partial section of the air pump across line 4-4 in FIG. 3;

FIG. 5 is a top view of an air pump in accordance with the prior art;

FIG. 6 is a side view of the air pump in FIG. 5; and

FIG. 7 is an enlarged bottom view in partial section of the air pump across line 7-7 in FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference to FIGS. 1 to 3, an air pump in accordance with the present invention comprises a main frame 10, a first pressure cylinder 11, a second pressure cylinder 12, an outlet device 13, a footboard 20, and a pressure relief device 30.

The main frame 10 has a front end and a rear end. The pressure cylinders 11, 12 are movably mounted in the main frame 10 at an interval and are parallel with each other, and each pressure cylinder 11, 12 has a connecting end and an outlet end. The connecting ends of the pressure cylinders 11, 12 are securely connected to the main frame 10 proximal to the rear end of the main frame 10.

The outlet device 13 is connected to and communicates with the outlet ends of the pressure cylinders 11, 12 near the front end of the main frame 10, and has two side faces and a check valve 14 mounted in the outlet device 13 near the first pressure cylinder 11 as shown in FIG. 4.

The footboard 20 is pivotally connected to the main frame 10, is securely connected to the pressure cylinders 11, 12 by a shaft, and has two side panels 21 and a limiting board 22. When the footboard 20 is moved relative to the main frame 10, the pressure cylinders 11, 12 are moved with the footboard 20 relative to the main frame 10. The side panels 21 are pivotally connected to the front end of the main frame 10, the side panels 21 each respectively face the pressure cylinders 11, 12 and also respectively face the side faces of the outlet device 13, and each side panel 21 has an inner surface. The limiting board 22 is mounted on the inner surface of a corresponding side panel 21 that faces the first pressure cylinder 11 to face a corresponding side face of the outlet device 13.

With further reference to FIGS. 3 and 4, the pressure relief device 30 is mounted on the outlet device 13 near the first pressure cylinder 11, and has a base 31, a ball 32, an adjusting rod 33 and an anti-slip-off element 34. The base 31 is securely mounted on the side face of the outlet device 13 that faces the limiting board 22, and has a leaking channel and an inner thread 35. The leaking channel is formed through the base 31, communicates with the outlet device 13 and has an internal surface. The inner thread 35 is formed around the internal surface of the leaking channel. The ball 32 is mounted in the leaking channel of the base 31.

The adjusting rod 33 is movably mounted in the leaking channel of the base 31 and has an inner end, an outer end, a head 36 and a body 37. The inner end of the adjusting rod 33 is mounted in the leaking channel of the base 31. The outer end of the adjusting rod 33 extends out of the base 31 and faces the limiting board 22. The head 36 is formed on and protrudes from the outer end of the adjusting rod 33. The body 37 is formed on the inner end of the adjusting rod 33, is formed with the head 36, and has an external surface and an outer thread 38. The outer thread 38 is formed around the external surface of the body 37 and is screwed with the inner thread 35 of the base 31. In addition, a length of the adjusting rod 33 that extends into the leaking channel of the base 31 is defined as L1.

The anti-slip-off element 34 may be a cap, is securely mounted around the head 36 of the adjusting rod 33, and has an outer side facing the limiting board 22. Furthermore, a distance between the limiting board 22 and the outer side of the anti-slip-off element 34 is defined as L2. In the present invention, the length L1 is longer than the distance L2.

During a pressure relief process of the pressure relief device 30 in accordance with the present invention, a user can rotate the anti-slip-off element 34 relative to the outlet device 13, and the adjusting rod 33 is rotated with the anti-slip-off element 34 relative to the base 31. Then, the body 37 of the adjusting rod 33 can be moved out of the base 31. When the adjusting rod 33 is rotated and is moved relative to the base 31, the outer thread 38 of the body 37 of the adjusting rod 33 is still screwed with the inner thread 35 the base 31 because the distance L2 between the anti-slip-off element 34 and the limiting board 22 is shorter than the length L1 of the adjusting rod 33 that extends into the base 31. Accordingly, the adjusting rod 33 will not be over-rotated and separated from the base 31 during the pressure relief process.

According to the above-mentioned features, the air pump in accordance with the present invention can prevent the adjusting rod 33 from being over-rotated during the pressure relief process by the limitation between the distance L2 and the length L1. Then, the outer thread 38 of the adjusting rod 31 is still screwed with the inner thread 35 of the base 31 to prevent the adjusting rod 31 from being separated from the base 31 and this is convenient in use.

Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

What is claimed is:
 1. An air pump comprising: a main frame having a front end and a rear end; a first pressure cylinder movably mounted in the main frame; a second pressure cylinder movably mounted in the main frame and being parallel with the first pressure cylinder at an interval; an outlet device connected to and communicating with the pressure cylinders near the front end of the main frame and having two side faces; and a check valve mounted in the outlet device near the first pressure cylinder: a footboard pivotally connected to the main frame, securely connected to the pressure cylinders and having two side panels pivotally connected to the front end of the main frame, the side panels each respectively facing the pressure cylinders and also each respectively facing the side faces of the outlet device, and each side panel having an inner surface; and a limiting board mounted on the inner surface of a corresponding side panel that faces the first pressure cylinder, and facing a corresponding side face of the outlet device; and a pressure relief device mounted on the outlet device near the first pressure cylinder and having a base securely mounted on the side face of the outlet device that faces the limiting board, the base having a leaking channel formed through the base, communicating with the outlet device, and having an internal surface; a ball mounted in the leaking channel of the base; an adjusting rod movably mounted in the leaking channel of the base and having an inner end mounted in the leaking channel of the base; and an outer end extending out of the base and facing the limiting board; an anti-slip-off element securely mounted around the outer end of the adjusting rod and having an outer side facing the limiting board; and wherein a length of the adjusting rod that extends into the leaking channel of the base is longer than a distance that is defined between the limiting board and the outer side of the anti-slip-off element.
 2. The air pump as claimed in claim 1, wherein the base has an inner thread formed around the internal surface of the leaking channel of the base; and the adjusting rod has a head formed on and protruding from the outer end of the adjusting rod; and a body formed on the inner end of the adjusting rod, formed with the head, and having an external surface and an outer thread formed around the external surface of the body and screwed with the inner thread of the base.
 3. The air pump as claimed in claim 2, wherein the head of the adjusting rod is mounted in the anti-slip-off element. 